Many types of screening machines include a door or a top cover which is movable relative to a frame or body, and which are clamped tight while the machine is in operation.
Screening machines are of course subjected to strong gyratory and vibrational forces in use, which can tend to loosen a screw clamp. If the clamp is not properly engaged, or if it is not held against rotation, the clamp may gradually loosen. This reduces the clamping force and, if continued, can cause the clamp to come off altogether or at least to permit escape of material being screened.
There has been a need for an adjustable self-locking hold-down clamp which is suitable for use on machinery subject to high vibration, such as screening machines.